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Field-squeeze operators via coherent population trapping
摘要： We present a scheme to generate unitarily two-mode and four-mode ?eld squeezing in optical cavities with the near-resonantly dressed three-level atoms in the (cid:2) con?guration. The dressing ?elds open two coherent population trapping (CPT) windows, within which the atoms stay predominantly in the dark state and yield strong nonlinearities for both the dressing ?elds themselves and the other applied ?elds. The two-mode squeeze operator is separated from degrees of freedom of atoms in a common CPT window, and the multimode squeeze operator is segregated in different CPT windows. The resulting two-mode and multimode interaction strengths are at least one order higher than in the previous dispersive schemes, where all ?elds are far off resonant with the atoms. The present near-resonant scheme is robust to spontaneous emission since atoms are nearly trapped in a long-lived superposition state.
关键词： field squeezing,coherent population trapping,optical cavities,quantum optics,three-level atoms
更新于2025-09-23 15:23:52
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Deterministic quantum state transfer between remote atoms with photon-number superposition states
摘要： We propose a protocol for quantum networking based on deterministic quantum state transfer between distant memory nodes using photon-number superposition states (PNSS). In the suggested scheme, the quantum nodes are single atoms con?ned in high-?nesse optical cavities linked by photonic channels. The quantum information written in a superposition of atomic Zeeman states of sending system is faithfully mapped through cavity-assisted Raman scattering onto PNSS of linearly polarized cavity photons. The photons travel to the receiving cavity, where they are coherently absorbed with unit probability creating the same superposition state of the second atom, thus ensuring high-?delity transfer between distant nodes. We develop this approach at ?rst for photonic qubit and show that this superposition state is no less reliably protected against the propagation losses compared to the single-photon polarization states, whereas the limitation associated with the delivery of more than one photon does not affect the process ?delity. Then, by preserving the advantages of qubits, we extend the developed technique to the case of state transfer by photonic qutrit, which evidently possesses more information capacity. This reliable and ef?cient scheme promises also a successful distribution of entanglement over long distances in quantum networks.
关键词： photonic qutrit,photonic qubit,quantum networking,quantum state transfer,entanglement distribution,optical cavities,Raman scattering,photon-number superposition states
更新于2025-09-23 15:21:01
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Cavity-Resonator-Integrated Guided-Mode Resonance Filters for Compact WDM Light Source
摘要： A cavity-resonator-integrated guided-mode resonance filter (CRIGF) consists of a grating coupler (GC) integrated in a waveguide cavity resonator on a transparent substrate, and shows a narrowband reflection spectrum for an incident free-space wave of a small diameter. CRIGF of the waveguide cavity formed by two distributed Bragg reflectors (DBRs) of different reflectances is discussed. Such a CRIGF can act as not only a wavelength-selective reflector but also an input waveguide coupler. Integration of such CRIGFs for different wavelengths in a waveguide is proposed to give an array of external mirrors and a wavelength division multiplexer for constructing a compact multi-wavelength light source. Four CRIGFs of 10-μm-size aperture with a wavelength spacing of 15 nm were fabricated and characterized. CRIGF integrated on a reflective layer via an optical buffer layer is also discussed. Optimization of reflective and buffer layers is theoretically investigated to maximize a waveguide-coupled lasing power.
关键词： gratings,waveguides,wavelength multiplexers,external mirrors,guided-mode resonance,waveguide couplers,optical cavities,wavelength filters
更新于2025-09-19 17:15:36
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[Institution of Engineering and Technology 20th Italian National Conference on Photonic Technologies (Fotonica 2018) - Lecce, Italy (23-25 May 2018)] 20th Italian National Conference on Photonic Technologies (Fotonica 2018) - Investigation of Methane Optical Sensor based on Absorption induced Redirection of Light Propagation in Coupled Cavities
摘要： Methane gas sensors are extremely important for explosion prevention in those industrial, commercial and domestic environments where the methane gas, being odorless, flammable and combustible with oxygen, may generate an explosion. In this paper we investigate a novel approach to methane optical sensors obtained by exploiting the variation of the propagation direction of the light induced by a change of the methane concentration. The sensor head is made by coupling a Fabry–Pérot (FP) cavity with a ring resonator. In particular, a change of the methane concentration varies the FP absorption coefficient that, in its turn, affects the relative optical power of the two counter-propagating optical beams, generated in the ring resonator. The ratio between the powers of the two counter-propagating optical beams, i.e. the contrast ratio (CR), has been evaluated for different volumetric concentrations of methane gas, up to 5%. This ratio decreases with methane gas concentration. In particular, when methane gas is absent, the CR is about 76 dB, whereas with a volumetric concentration of 1% of methane gas, the CR is about 32.7 dB. For a methane gas concentration of 5% (equal to its lower explosive limit), the CR is reduced to 18.6 dB.
关键词： Gas optical sensor,Coupled optical cavities,Fiber optic sensors
更新于2025-09-16 10:30:52